US 6991644 B2
The invention comprises a system and method for treating an exposed tissue of a patient with a light energy. A plurality of light emitting devices are optically coupled with a patients tissue, and apply light treatments to the tissue. A driver circuit and a controller operate to drive the light emitting devices to output different intensities of light treatment to different sub-areas of the tissue being treated.
1. A method for treating an area of tissue, where the area of tissue includes a plurality of different sub-areas of tissue which have different characteristics:
providing a plurality of light emitting devices optically coupled with the area of tissue, wherein the light emitting devices are configured into different regions, where different sub-areas of tissue having different characteristics correspond to different regions of light emitting diodes;
sensing an amount of light reflected from each of the different sub-areas;
driving a first region of the plurality of light emitting devices to output a first light treatment to a first sub-area of tissue, wherein the first light treatment is determined based on a first amount of light reflected from the first sub-area; and
driving a second region of the plurality of light emitting devices to output a second light treatment to a second sub-area of tissue, wherein the second light treatment is determined based on a second amount of light reflected from the second sub-area of tissue.
2. The method of
3. The method of
4. The method of
5. The method of
6. The method of 1, wherein the first light treatment provides for a first level of irradiance for the first sub-area, and the second light treatment provides for a second level or irradiance for the second sub-area and the second level of irradiance is less that the first level or irradiance.
7. The method of
8. A method for treating an area of tissue, where the area of tissue includes a plurality of different sub-areas of tissue which have different amounts of pigmentation:
sensing an amount of light reflected from each of the plurality of different sub-areas; and
applying a light treatment to the area of tissue, based on the amount of light reflected from each of the plurality of different sub-areas, wherein the light treatment operates to reduce differences in the amount of pigmentation in different sub-areas of tissue.
9. The method of
generating a first amount of light to apply a first light treatment to a first sub-area of the area of tissue; and
generating a second amount of light to apply a second light treatment to a second sub-area of the area of tissue.
10. The method of
applying a first amount of light energy to a first group of sub-areas of tissue of the area of tissue, where the first group of sub-areas of tissue have less pigmentation, than a second group of sub-areas of tissue to which the first amount of light energy is not applied.
11. The method of
12. The method of
13. The method of
This patent application claims the benefit of U.S. Provisional Application No. 60/432,935, filed Dec. 12, 2002, which is incorporated herein by reference.
The present invention provides for spatially selective phototherapy using LEDs.
A number of diseases, medical or trauma conditions give rise to cosmetically undesirable pigmentary variation in human skin. Scars, temporary or permanent hypo- and hyper-pigmentation, striae (stretch marks), leukoderma, poikiloderma of Civatte, etc., are examples of conditions in which a melanin pigmentation cosmetic defect is presented by at least one component of the condition. A variety of approaches have been used to reduce the contrast between pigment variation regions, including chemical etches (“peel”), dermabrasion, laser ablation, and UV light sources.
Prior approaches for dealing with these conditions included removing the abnormally pigmented skin, or a portion of such skin with the goal of promoting new growth that contains cosmetically desirable “natural” pigmentation. Another approach provided for treating skin with UV light sources to promote the formation of melanin in melanin-deficient skin.
Ablative laser skin resurfacing, chemical peels and dermabrasion are examples of some approaches used for removing skin. UV lamps and excimer laser therapies are examples of some types of UV light sources.
Prior approaches have suffered from a lack of good control over the pigment induction. One shortcoming frequently associated with removing abnormally pigmented skin is that pigment-deficient areas of skin frequently exhibit resistance to melanogenesis or pigment induction. Thus, even after removing a portion of the pigment-deficient area of skin, and generating new growth of skin, the pigment deficiency frequently persists. In connection with providing UV treatment to pigment deficient skin, difficulties are also realized in that the spatial localization of the treatment is difficult to control and results in less than desirable outcomes.
Generally desirable characteristics of a phototherapeutic approach to pigmentary induction would include: (i) production of a temporary-to-permanent pigmentary darkening in various skin phototypes; and (ii) an ability to target discrete and localized non-uniformities and “blend” them to produce a more uniform pigment background. An embodiment herein provides for controlling the exposure to light, so that the treatment does not result in just increasing an overall pigment background by a uniform amount (e.g. merely increasing a base level of all pigment in a treatment area). For example, an embodiment herein can provide for a relatively large area UV exposure with some type of masking, or directing a UV point source at a specific local target.
A system of an embodiment of the present invention is shown in
The array module 102 includes a surface structure 106 to which the LEDs are mounted. This surface structure could be formed on a printed circuit board which contains conductive paths from the LEDs 104 to a larger passive heat sink, or active cooler 120, such as water channel cooled plate. Typical heat loading from dissipation by LEDs in such an array is <1W/cm2. For arrays containing 1000 or more LEDs, such heat loading can be in the 100's of Watts.
An umbilical supply cord 108 containing the driving current lines, temperature sensor, optical sensor and potentially low flow water for active cooling connects the array module 102 and LEDs 104 with the drive electronics console 110. Additional details of the console are shown in
An embodiment herein provides cosmetically desirable pigmentation in the skin in a spatially and temporally controlled manner. Melanin synthesis in melanocytes, or “melanogenesis”, refers to this process. Melanogenesis can take place as a photoprotective effect in response to UV radiation, and when it occurs in response to natural or artificial UV light, it is referred to as “tanning.”
A distinct phenomenon associated with true melanogenesis also occurs upon exposure to UV and visible light. “Immediate pigment darkening” (IPD) is a transient oxidative change to the state of existing melanin, occurs mostly in darker skin phototypes. The persistence of IPD is hours to days, and is not clinically useful in itself for treating pigmentation cosmetic problems. Strong IPD in dark skin phototypes indicates that longer term (days to onset) melanogenesis will take place, and may serve as a clinical endpoint to pigmentation phototherapy. Additional discussion related to this issue is provided by, Kollias N, Malallah Y H, Al-Ajmi H, Baqer A, Johnson B E, Gonzales S. Erythema and melanogenesis action spectra in heavily pigmented individuals as compared to fair-skinned Caucasians, Photodermatol Photoimmunol Photomedicine 1996: 12: 183–188, which is incorporated herein by reference in its entirety.
As shown in
From a practical standpoint one must recognize that there are some issues that need to be addressed in connection with using LEDs. At present LED performance is best in the visible and infrared, and falls rapidly at the shorter wavelengths of the UVA range. An example of a high performance UV LED commercially available are the NSHU550A and NSHU590A from Nichia Corporation, Japan. These parts provide 2.0 and 1.4 mW of UVA light centered at 375 nm, respectively. In fact, at present, commercial devices below 360 nm are not readily available. Choosing appropriate LED devices becomes a trade-off between shorter wavelengths that are more effective, and longer wavelengths at which efficient and practical LED devices can be obtained.
Reasonably high flux devices with a central emission band below 400 nm and above 365 nm can be obtained using some currently available LEDs. The MMD's in this band are in the low 100's of J/cm2. For treatments that are reasonably short duration (<1 hr total), and are somewhat above the MMD (for example, 500J/cm2), irradiances of at least 100 mW/cm2 are desired. Close packed arrays of sub-400 nm devices are commercially available (one example the Shark OTL-395A-5-10-66 available from OptoTech, Inc. Wheeling, Ill.). At distances of a few millimeters, these arrays provide measured irradiances of up to 200 mW in an approximately 1 cm2 emitting area. The wavelength center of this array was measured to be 395 nm. An arrangement of such LED arrays in close proximity to a person's skin can be used to produce a uniformly high irradiance of near-UVA, sub-400 nm illumination field. Similarly, the LEDs provided by Nichia Corporation, which can be obtained in 5 mm diameter packages, can be used to produce as much as 5 mW/cm2 of 375 nm light on skin. The approximately 20× reduction in irradiance with these LEDs compared to the example above is partially offset by the factor of 3 decrease in the MMD required at this somewhat shorter wavelength, as is illustrated in
Experiments have been performed using a 410 nm LED arrays to treat a patient's face. While melanogenesis is not expected to occur in this waveband, treatment of a dark phototype skin showed obvious IPD after 30 minutes of treatment at approximately 80 mW/cm2 (140J/cm2 dose). IPD maximum sensitivity falls between 320 and 380 nm.
Implementation of system 100 with an array module 102 using 395 nm LEDs arrays should reach the MMD in less than 1 hour of treatment time over a broad treatment area. In embodiment the array module 102 would use approximately 1000 individual LED devices in an array that is designed to treat approximately 50 cm2 area of the face or back, and drives the entire array at approximately 6A and 45V, or ˜300W.
The consequence is that the delivered irradiance is lower than a system where all of the LEDS are subject to a single control and drive current. This reduction depends on the array size, and can be reduced by addressing entire rows or small blocks or regions of LEDs, rather than individual devices.
The addressable UVA LED array 402 is positioned so that it is adjacent to the patient's skin 408 which is to be treated. The white regions 410 in the skin represent low melanin content in skin. The areas 412 and 414 represent irradiance which would be delivered from an LED when current is supplied to the particular LED to drive the device. As shown the darker areas 414 correspond to LEDs which would receive higher current and emit higher energy amounts of UVA to the pigment deficient areas of skin 410. In this embodiment, advance knowledge of the desired spatial profile of the treatment dosage or irradiance is required. In operation, an area of the patient's skin which is to be treated would be mapped, and the information would be input to the controller 116 in the electronic console 110. The controller 116 would then cause the driver circuit 112 of the electronic console 110 to output current to regions of LEDS which are positioned to emit UVA to the pigment deficient area of the skin, and other areas which are not pigment deficient would not receive a driving current. It should be noted that depending on the actual implementation each addressable LED region could consist or one or more LEDs.
Ideally the LED array would be such that it is capable of providing very high resolution, so that it can provide UVA to those areas which are pigment deficient. In some cases, pigment deficient areas can be as narrow as 1 mm wide.
The light from LEDs 504 may serve as the backscattered light that the photodetector 508 senses. In this case, the lack of pigment causes a higher proportion of the UVA light to be backscattered relative to the more UVA-absorbing pigment bearing regions Another embodiment could provide for populating the LED array with a number of alternate wavelength LEDs, where the wavelength of the alternate LEDs could be chosen for maximum contrast in the amount of absorption between pigmented and hypo-pigmented regions (400–550 nm light would be suitable candidate for this purpose—see
In one embodiment the photodetector signals serve as the basis of a control loop for determining the exposure for a given area of skin, and an array of LEDs delivers the appropriate dose profile. In one version, the feedback or servo mechanism is determined at the beginning of treatment, and is not necessarily dynamic. That is, the initial pigment profile determines the spatial profile of the treatment dosing. In still another embodiment, instead of measuring differences only between initial pigmentation, the photodetector array senses dynamically the changes in remittance due to immediate pigment darkening IPD detection, which can then be used to determine the end point of exposure. This can be done in a spatially localized way, as above, or it can be used to determine the end of the overall treatment.
Further, it is helpful to recognize that the spectral remittance for dark and light human skin is different. Indeed some prior works have specifically compared dark and light skin phototypes, and developed data showing the difference in the relative amount of UVA-visible light which is backscattered. See e.g. R. R. Anderson and J. A. Parrish, Optical Properties of Human Skin, p. 159–193, The Science of Photomedicine, 1982, which is incorporated herein by reference in its entirety. See also the data shown in
In the system 600 of
The bundle 610 is then placed in near contact with the skin. Actual contact of the bundle or associated delivery against the skin could desirably be minimized. UVA-driven melanogenesis is very strongly dependent on circulatory oxygen. That is, pressing on skin with, say, a window, during phototreatment with a UVA source could drop the response by as much as 10×. See e.g., Auletta M, Gange R W, Tan O T, Matzinger E. Effect of Cutaneous Hypoxia upon erthyma and pigment responses to UVA, UVB and PUVA (8-MOP+UVA) in Human Skin. J Invest Dermatol 86: 649–652, 1986; which is incorporated herein by reference in its entirety, and discusses the effect of circulatory oxygen on phototreatment.
Coupling visible LEDs into large core fibers can result in up to 30% of the light emitted from a domed LED being captured. As multi-milliWatt LEDs in the 365–375 nm range come available, it will be possible to create bundles using fiber coupling to produce irradiances at the bundle output of tens of milliWatts/cm2, sufficient to induce melanogenesis in reasonable treatment times.
An additional advantage of the overall fiber bundle approach is that the light treatment handpiece or delivery system can be small and located far from the actual electronics and light generating array(s).
Additionally a bundle of fibers or light pipes can be further concentrated, with substantial loss of power, by a secondary guide or reflector. Advantages of this approach include the ability to treat small regions by a hand-applied tip, and the use of even higher irradiances than direct arrays or bundled fibers (as much as 100 mW/cm2 of 365–375 nm may be possible.
Although specific embodiments and methods of the present invention are shown and described herein, this invention is not to be limited by these methods and embodiments. Rather, the scope of the invention is to be defined by the following claims and their equivalents.